S-Adenosylmethionine (SAMe) and N-acetylcysteine (NAC), two agents with known benefit for reducing hepatic injury, were used to treat ischemic injury in a rat liver perfusion model. We compared cold ischemic injury with sequential periods of cold and warm ischemia that equate to episodes during the storage and implantation of liver grafts. The additional period of 20 min warm ischemia after 24 hr cold ischemia profoundly impaired initial (15 min) mean blood flow (1.8 +/- 0.1 vs. 2.7 +/- 0.4 ml/min/g liver for cold ischemia, P < 0.001) and bile flow (2.31 +/- 0.74 vs. 10.6 +/- 3.96 mg/hr/g liver for cold ischemia, P < 0.001) and increased the oxygen extraction ratio (OER) (0.53 +/- 0.03 vs. 0.29 +/- 0.08 for cold ischemia, P < 0.01) and acid release from glycolysis (0.18 +/- 0.02 vs. 0.11 +/- 0.02 mmol/g liver for cold ischemia, P < 0.05). Impairment of blood flow, bile flow, and OER was sustained throughout the 3-hr perfusion. In the same model, SAMe restored hepatic blood flow to control values when administered to the donor, included in the UW, and added as a bolus to the perfusate on reperfusion. SAMe also improved OER (P < 0.001 vs. sequential cold and warm ischemia) and initial bile flow (9.63 +/- 2.01 mg/hr/g liver, P < 0.01), returning values to control levels by 3 hr. SAMe reduced the initial release of glucose upon reperfusion (P < 0.01) and improved subsequent glucose uptake, but corresponding benefits on enzyme release from damaged hepatocytes (AST) or endothelial cells (purine nucleoside phosphorylase) were not observed. Equimolar concentrations of NAC induced transitory improvements in blood and bile flow but these were not sustained beyond 30 min of reperfusion.